Here is my 100% Achievement guide for Without Escape!
Once in the other dimension, there is a clock puzzle you have to solve.
You find these huge array of clocks where your TV once was in the living room.
Once there, the first puzzle you have to input "4:35"
For the second time you have to input a time it is "7:45"
Interact with the Ear on the big mirror right next to you to get the key and achievement!
Go to 10:05 in the video to see what and where it is done.
Hope this helps!